1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a write (recording) head having an induction-type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a write head. To achieve this, it is required to implement a write head of a narrow track structure wherein the width of top and bottom poles sandwiching the write gap layer on a side of the air bearing surface is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to FIG. 34A to FIG. 37A and FIG. 34B to FIG. 37B to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a method of manufacturing a thin-film magnetic head of related-art. FIG. 34A to FIG. 37A are cross sections each orthogonal to an air bearing surface of the thin-film magnetic head. FIG. 34B to FIG. 37B are cross sections of pole portions of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 34A and FIG. 34B, an insulating layer 202 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 201 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 202 a bottom shield layer 203 made of a magnetic material is formed for making a read head.
Next, on the bottom shield layer 203, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 204 as an insulating layer. On the bottom shield gap film 204 an MR element 205 for reading having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 206 are formed on the bottom shield gap film 204. The electrode layers 206 are electrically connected to the MR element 205.
Next, a top shield gap film 207 is formed as an insulating layer on the bottom shield gap film 204 and the MR element 205. The MR element 205 is embedded in the shield gap films 204 and 207.
Next, on the top shield gap film 207, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 208 having a thickness of about 3 xcexcm is formed. The bottom pole layer 208 is made of a magnetic material and used for both a write head and a read head.
Next, as shown in FIG. 35A and FIG. 35B, on the bottom pole layer 208, a write gap layer 209 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed. Next, a portion of the write gap layer 209 is etched to form a contact hole 209a to make a magnetic path. On the write gap layer 209 in the pole portion, a top pole tip 210 made of a magnetic material and having a thickness of 0.5 to 1.0 xcexcm is formed for the write head. At the same time, a magnetic layer 219 made of a magnetic material is formed for making the magnetic path in the contact hole 209a for making the magnetic path.
Next, as shown in FIG. 36A and FIG. 36B, the write gap layer 209 and the bottom pole layer 208 are etched through ion milling, using the top pole tip 210 as a mask. As shown in FIG. 36B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 210), the write gap layer 209, and part of the bottom pole layer 208 are formed vertically in a self-aligned manner.
Next, an insulating layer 211 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 211 is then polished to the surfaces of the top pole tip 210 and the magnetic layer 219 and flattened.
Next, on the flattened insulating layer 211, a first layer 212 of a thin-film coil is made of copper (Cu), for example, for the induction-type write head. Next, a photoresist layer 213 is formed into a specific shape on the insulating layer 211 and the first layer 212. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 213. On the photoresist layer 213, a second layer 214 of the thin-film coil is then formed. Next, a photoresist layer 215 is formed into a specific shape on the photoresist layer 213 and the second layer 214. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 215.
Next, as shown in FIG. 37A and FIG. 37B, a top pole layer 216 is formed for the write head on the top pole tip 210, the photoresist layers 213 and 215, and the magnetic layer 219. The top pole layer 216 is made of a magnetic material such as Permalloy. Next, an overcoat layer 217 of alumina, for example, is formed to cover the top pole layer 216. Finally, machine processing of the slider including the foregoing layers is performed to form the air bearing surface 218 of the thin-film magnetic head including the write head and the read head. The thin-film magnetic head is thus completed.
FIG. 38 is a top view of the thin-film magnetic head shown in FIG. 37A and FIG. 37B. The overcoat layer 217 and the other insulating layers and insulating films are omitted in FIG. 38.
In FIG. 37A, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. The throat height is the length (height) of portions of magnetic pole layers facing each other with the write gap layer in between, between the air-bearing-surface-side end and the other end. The MR height is the length (height) between the air-bearing-surface-side end of the MR element and the other end. In FIG. 37B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the write track width. In addition to the throat height, the MR height and so on, the apex angle as indicated with xcex8 in FIG. 37A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coil covered with the photoresist layers 213 and 215. The apex angle is the angle formed between the top surface of the insulating layer 211 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, apex angle xcex8, and track width P2W as shown in FIG. 37A and FIG. 37B.
To achieve high areal recording density, that is, to fabricate a write head with a narrow track structure, it has been particularly required that track width P2W fall within the submicron order of 1.0 xcexcm or smaller. It is therefore required to process the top pole into the submicron order through semiconductor process techniques.
A problem is that it is difficult to form the top pole layer having small dimensions on the apex.
As disclosed in Published Unexamined Japanese Patent Application Hei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied to the top of the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 xcexcm or greater. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm over the apex, a photoresist film having a thickness of 8 to 10 xcexcm or greater, for example, is formed below the apex since the fluid photoresist goes downward.
To implement a write track width of the submicron order as described above, it is required to form a frame pattern having a width of the submicron order through the use of a photoresist film. Therefore, it is required to form a fine pattern of the submicron order on top of the apex through the use of a photoresist film having a thickness of 8 to 10 xcexcm or greater. However, it is extremely difficult to form a photoresist pattern having such a thickness into a reduced pattern width, due to restrictions in a manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the base electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may go out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern.
As thus described, it is difficult in prior art to fabricate the top pole layer with accuracy if the pole width of the submicron order is required.
To overcome the problems thus described, a method has been taken, as shown in the foregoing example of related-art manufacturing steps illustrated in FIG. 35A to FIG. 37A and FIG. 35B to FIG. 37B. In this method, a track width of 1.0 xcexcm or smaller is formed through the use of the top pole tip 210 effective for making a narrow track of the write head. The top pole layer 216 to be a yoke portion connected to the top pole tip 210 is then fabricated (as disclosed in Published Unexamined Japanese Patent Application Showa 62-245509 [1987] and Published Unexamined Japanese Patent Application Showa 60-10409 [1985]). That is, the ordinary top pole layer is divided into the top pole tip 210 and the top pole layer 216 to be the yoke portion in this method. As a result, it is possible that the top pole tip 210 that defines the write track width is formed to have small dimensions to some degree on the flat top surface of the write gap layer 209.
In Published Unexamined Japanese Patent Application Heisei 6-314413, a thin-film magnetic head is disclosed in which each of the top pole layer and the bottom pole layer is made up of two layers that are a layer including the pole portion and a layer to be the yoke portion.
However, in the thin-film magnetic head shown in FIG. 37A and FIG. 37B, and in the head disclosed in Published Unexamined Japanese Patent Application Heisei 6-314413, the end face of the layer to be the yoke portion is exposed from the air bearing surface. As a result, writing may be performed by the thin-film magnetic head not only on a side of the layer including the pole portion but also on a side of the layer to be the yoke portion, and so-called xe2x80x98side writexe2x80x99 may result, that is, data is written in a region of a recording medium where data is not supposed to be written.
In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-314413, the portions of the total of four layers located in the pole portions, that is, the two layers of the top pole layer and the two layers of the bottom pole layer, have equal widths. To form the portions of the four layers located in the pole portions that have equal widths, each of the layers may be formed such that the shape of the portion of each of the layers located in the pole portions is determined when each of the layers is fabricated. Alternatively, the four layers may be formed and then etched at the same time such that the portions of the four layers located in the pole portions have equal widths.
However, if each of the layers is formed such that the shape of the portion of each of the layers located in the pole portions is determined when each of the layers is fabricated, it is difficult to determine the shape of the portion of each of the layers located in the pole portions with accuracy and to align the portions of the layers located in the pole portions with accuracy, particularly when the write track width is reduced.
If the four layers are etched at the same time, it takes a long time to etch and it is difficult to determine the shapes of the portions of the four layers located in the pole portions with accuracy.
Furthermore, in a prior-art thin-film magnetic head, it is difficult to reduce the magnetic path (yoke) length. That is, if the coil pitch is reduced, a head with a reduced yoke length is achieved and a write head having an excellent high frequency characteristic is achieved, in particular. However, if the coil pitch is reduced to the limit, the distance between the zero throat height level (the level of the air-bearing-surface-side end of the insulating layer that defines the throat height) and the outermost end of the coil is a major factor that prevents a reduction in yoke length. Since the yoke length of a two-layer coil can be shorter than that of a single-layer coil, a two-layer coil is adopted to many of write heads for high frequency application. However, in the prior-art magnetic head, a photoresist film having a thickness of about 2 xcexcm is formed to provide an insulating film between coil layers after a first layer is formed. Consequently, a small and rounded apex is formed at the outermost end of the first layer of the coil. A second layer of the coil is then formed on the apex. The second layer is required to be formed on a flat portion, because it is impossible to etch the seed layer of the coil in the sloped portion of the apex and the coil is therefore shorted.
Therefore, if the total coil thickness is 2 to 3 xcexcm, the thickness of the insulating film between the layers of the coil is 2 xcexcm, and the apex angle is 45 to 55 degrees, for example, the yoke length is required to be 6 to 8 xcexcm which is twice as long as the distance between the outermost end of the coil and the neighborhood of the zero throat height level, that is, 3 to 4 xcexcm (the distance between the innermost end of the coil and the portion where the top and bottom pole layers are in contact with each other is required to be 3 to 4 xcexcm, too), in addition to the length of the portion corresponding to the coil. This length of the portion other than the portion corresponding to the coil is one of the factors that prevent a reduction in yoke length.
Assuming that a two-layer eleven-turn coil wherein the line width is 1.2 xcexcm and the space is 0.8 xcexcm is fabricated, for example, the portion of the yoke length corresponding to the first layer 212 of the coil is 11.2 xcexcm, if the first layer is made up of six turns and the second layer is made up of 5 turns, as shown in FIG. 37A and FIG. 37B. In addition to this length, the total of 6 to 8 xcexcm, that is, the distance between each of the outermost and innermost ends of the first layer 212 of the coil and each of ends of the photoresist layer 213 that insulates the first layer 212, is required for the yoke length. Therefore, the yoke length is 17.2 to 19.2 xcexcm. If an 11-turn coil is made up of one layer, the yoke length is 27.2 to 29.2 xcexcm. In the present patent application, the yoke length is the length of a portion of the pole layer except the pole portion and the contact portions, as indicated with L0 in FIG. 37A. As thus described, it is difficult in the prior art to further reduce the yoke length, which prevents improvements in high frequency characteristic.
It is a first object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for forming the pole portions of the induction-type electromagnetic transducer with accuracy and for preventing writing of data in a region in which data is not supposed to be written.
It is a second object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for achieving a reduction in yoke length, in addition to the first object.
A thin-film magnetic head of the invention comprises: a medium facing surface that faces toward a recording medium; a read head incorporating: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, the first and second shield layers having portions that are located on a side of the medium facing surface and opposed to each other, the magnetoresistive element being located between these portions; and a write head incorporating: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The first magnetic layer is located closer to the read head than the second magnetic layer. The first magnetic layer includes: a first pole portion layer that includes the pole portion of the first magnetic layer and has surfaces one of which is adjacent to the gap layer; and a first yoke portion layer that is a yoke portion of the first magnetic layer and connected to the other surface of the first pole portion layer. An end of the first yoke portion layer that faces toward the medium facing surface is located at a distance from the medium facing surface.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a read head; and a write head. In the thin-film magnetic head the read head incorporates: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, the first and second shield layers having portions that are located on a side of the medium facing surface and opposed to each other, the magnetoresistive element being located between these portions. The write head incorporates: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The first magnetic layer is located closer to the read head than the second magnetic layer.
The method of manufacturing the thin-film magnetic head of the invention comprises the steps of: forming the read head; forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the coil such that the at least part of the coil is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The step of forming the first magnetic layer includes formation of: a first pole portion layer that includes the pole portion of the first magnetic layer and has surfaces one of which is adjacent to the gap layer; and a first yoke portion layer that is a yoke portion of the first magnetic layer and connected to the other surface of the first pole portion layer. An end of the first yoke portion layer that faces toward the medium facing surface is located at a distance from the medium facing surface.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the first magnetic layer includes the first pole portion layer and the first yoke portion layer. In addition, the end of the first yoke portion layer that faces toward the medium facing surface is located at a distance from the medium facing surface. As a result, it is possible to form the first pole portion layer of the first magnetic layer with accuracy, and it is thereby possible to form the pole portion with accuracy. According to the invention, the end of the first yoke portion layer that faces toward the medium facing surface is located at a distance from the medium facing surface, so that writing of data in a region where data is not supposed to be written is prevented.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the first pole portion layer may include a portion that has a width equal to a track width and that has an end located in the medium facing surface.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the first pole portion layer may include: a first portion that has a width equal to a track width and has an end located in the medium facing surface; and a second portion that has a width greater than the track width and is located farther from the medium facing surface than the first portion.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, an insulating layer encasing portion and a throat height defining insulating layer may be provided. In the encasing portion the throat height defining insulating layer that defines a throat height is placed, the encasing portion being formed in the first pole portion layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the at least part of the thin-film coil may be located on a side of the first pole portion layer. In this case, it is possible to provide a coil insulating layer that covers the at least part of the coil located on the side of the first pole portion layer and has a surface facing toward the gap layer, the surface being flattened together with the surface of the first pole portion layer adjacent to the gap layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the second magnetic layer may include: a second pole portion layer that includes the pole portion of the second magnetic layer and has surfaces one of which is adjacent to the gap layer; and a second yoke portion layer that is a yoke portion of the second magnetic layer and connected to the other surface of the second pole portion layer. In addition, an end of the second yoke portion layer that faces toward the medium facing surface may be located at a distance from the medium facing surface.
In this case, each of the first and second magnetic layers includes the pole portion layer and the yoke portion layer, and the end of each of the yoke portion layers that faces toward the medium facing surface is located at a distance from the medium facing surface. It is therefore possible to form the two pole portion layers with accuracy, and it is thereby possible to form the pole portions with accuracy. In this case, the end of each of the yoke portion layers that faces toward the medium facing surface is located at a distance from the medium facing surface, so that writing of data in a region where data is not supposed to be written is prevented.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, each of the first and second pole portion layers may include a portion that has a width equal to a track width and has an end located in the medium facing surface.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, at least one of the first and second pole portion layers may include: a first portion that has a width equal to a track width and has an end located in the medium facing surface; and a second portion that has a width greater than the track width and is located farther from the medium facing surface than the first portion.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, it is possible to provide: an insulating layer encasing portion in which a throat height defining insulating layer that defines the throat height is placed, the encasing portion being formed in one of the first and second pole portion layers; and the throat height defining insulating layer that is placed in the insulating layer encasing portion.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the at least part of the thin-film coil may be located on a side of the second pole portion layer. In this case, it is possible to provide a coil insulating layer that covers the at least part of the coil located on the side of the second pole portion layer and has a surface facing toward the second yoke portion layer, the surface being flattened together with the surface of the second pole portion layer that faces toward the second yoke portion layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the at least part of the thin-film coil may be located on a side of the first pole portion layer, and the second magnetic layer is made up of one layer including a portion that defines a track width.
In this case, the at least part of the coil is located on a side of the first pole portion layer, so that it is possible that the second magnetic layer made up of the one layer is made flat or nearly flat, and the pole portion is formed with accuracy.
Other and further objects, features and advantages of the invention will appear more fully from the following description.